Field
The disclosed concept relates to electrical switching apparatus, such as, for example, circuit breakers. The disclosed concept further relates to slot motors for circuit breakers. The disclosed concept also relates to enclosures for slot motors.
Background Information
Electrical switching apparatus, such as circuit breakers, are employed in diverse capacities in power distribution systems. A circuit breaker may include, for example, a line conductor, a load conductor, a fixed contact and a movable contact, with the movable contact being movable into and out of electrically conductive engagement with the fixed contact. This switches the circuit breaker between an ON or closed position and an OFF or open position, or between the ON or closed position and a tripped or tripped OFF position. The fixed contact is electrically conductively engaged with one of the line and load conductors, and the movable contact is electrically conductively engaged with the other of the line and load conductors. The circuit breaker may also include an operating mechanism having a movable contact arm upon which the movable contact is disposed.
In order to enhance the speed of separation of the separable contacts, the contacts may be disposed within a slot motor, which increases interruption performance. Slot motors typically include a number of plates (e.g., laminations) composed of magnetically permeable material (e.g., steel), which surrounds the separable contacts and the movable contact arm of the circuit breaker. When the power circuit is live, an electrical arc may be drawn between the separable contacts during separation. The electrical current interacts electromagnetically with the slot motor to induce a magnetic field in the magnetic material of the slot motor, which, in turns, interacts with the separating contacts and the movable contact arm to accelerate the contact opening process.
Known slot motors include support members that protect respective steel laminations on one side of the steel laminations. During assembly, operators manually apply tape to opposing sides of the steel laminations. Applying tape is labor intensive and reduces productivity. Also, if applied incorrectly, the steel laminations can be exposed, resulting in dielectric breakdown after repeated interruptions. This in turn could cause an arc restrike, resulting in a failure of the circuit breaker to interrupt.
There is thus room for improvement in electrical switching apparatus, and in slot motors and enclosures therefor.